Residential alarm system

ABSTRACT

Circuitry is disclosed for sounding an alarm horn when a window or door is opened, and an associated limit switch is closed, the circuitry providing for predetermined time delays suitable for use in either one of two possible modes of operation. A console is provided in the residence to be protected, and contains a battery power source for operating the circuitry, a key control switch, and a mode selector switch. One mode is suitable for use at night when the occupant of the residence is at home, and the circuitry provides for a time delay in sounding the alarm following closing of one of the limit switches, in order to allow the occupant time to close any open exit door or window. The second mode is for use when the occupant leaves his residence unattended, and two time delays are provided for in this second mode prior to sounding any alarm, and after switching the system on. One of these delays is the same as that outlined above, the other delay being of variable duration and in sequence with the first mentioned delay. The occupant has the same nine seconds to re-enter and deactivate the system once he has left his residence, but he also has the benefit of a secondary delay on leaving his residence. Thus, he may activate the system in mode two, open an exit door within a certain time, and procrastinate for any amount of time before leaving and closing the door behind him. Having closed the door behind him he will have the benefit of a short delay on re-entry to allow him to deactivate the system.

United States Patent [191 Dobrzanski et al.

[ RESIDENTIAL ALARM SYSTEM [75] Inventors: John J. Dobrzanski, NewBritain,

Conn.; Willaim J. Doyle,'La Habra, Calif.

[73] Assignee: Emhart Corporation, Bloomfield,

Conn.

22 Filed: July 12,1972

21 Appl. No.: 271,110

Primary Examiner-John W. Caldwell Assistant Examiner-Scott F. PartridgeAttorney, Agent, or Firm-McCormick, Paulding & Huber [57] ABSTRACTCircuitry is disclosed for sounding an alarm horn when 1451 Apr. 9, 1974a window or door is opened, and an associated limit switch'is closed,the circuitry providing for predetermined time delays suitable for usein either one of two possible modes of operation. A console is providedin the residence to be protected, and contains a battery power sourceforoperating the circuitry, a key control switch, and a mode selectorswitch. One mode is suitable for use at night when the occupant of theresidence is at home, and the circuitry provides for a time delay insounding the alarm following closing of one of the limit switches, inorder to allow the occupant time to close any open exit door or window.The second mode is for use when the occupant leaves his residenceunattended, and two time delays are provided for in this second modeprior to sounding any alarm, and after switching the system on. One ofthese delays is the same as that outlined above, the other delay beingof variable duration and in sequence with the first mentioned delay. Theoccupant has the same nine seconds to re-enter and deactivate the systemonce he has left his residence, but he also has the benefit of asecondary delay on leaving his residence. Thus, he may activate thesystem in mode two, open an exit door within a certain time, andprocrastinate for any amount of time before leaving and closing the doorbehind him. Having closed the door behind him he will have the benefitof a short delay on re-entry to allow him to deactivate the system.

5 Claims, 1 Drawing Figure RESIDENTIAL ALARM SYSTEM SUMMARY OF INVENTIONThis invention relates to residential alarm systems, and deals moreparticularly with a circuit capable of two modes of operation, one foruse when the occupant is at home, and the second when he intends toleave, and return at a later time.

Normally closed sensor switches are mounted at the various doors andwindows, and these switches are held open when these various exitopenings are suitably secured. A control console located inside theresidence contains a battery, a mode selector switch, and a keylockcontrol switch for energizing circuitry which includes these sensorswitches arranged in parallel.

The system also includes an alarm device, selectively operated from thebattery by a sensing circuit, and the sensing circuit has solid stategate means which can be triggered following a known delay by a thresholddevice. The sensing switches are preferably arranged between aresistance-capacitance grouping associated with and the gate, in orderto minimize drain on the battery when the system is operating, and topermit the alarm to operate only after a known delay following reclosingof the sensing switch in the second mode. This feature permits theoccupant to close the keylock or control switch allowing him time toopen one of his exit doors within the known delay period, and to thenhave an undetermined length of time within which to exit and reclose thedoor. Once the door, or any other secured opening has been tamperedwith, reclosing an associated sensing switch, the alarm device willoperate normally, that is with the limited delay period built into thecircuit as described above.

In both mode one and in mode two following the above preliminarysituation, the alarm will be energized from the battery following thebrief delay dictated in mode one, and in mode two be a secondary gateand triggering circuit network.

BRIEF DESCRIPTION OF THE DRAWING The single view shows in schematicfashion the circuitry included in an alarm system constructed inaccordance with 'the present invention.

DETAILED DESCRIPTION In order to equip a typical residence with aburglar alarm system in accordance with the present invention, aplurality of normally closed limit switches, or other sensing deviceswith contacts arranged so as to close in response to a condition to bedetected, are provided at the various exits and windows of the residenceto be secured in such a way as to close when the exit door or window isopened or otherwise tampered with. As shown in FIG. 1 these. sensingdevices may comprise limit switches, such as LS l and LS 2, arranged inparallel with respect to one another, or may comprise contactsengageable by a deadbolt, or latch bolt, or may comprise contacts in amagnetic motion detector or sensor or any other known intrusion device.Such devices will be arranged so as to be held in a normally opencircuit condition, and are adapted to close whenever the securedcondition is violated. The electrical connection of these devices, inparalleL'back to a control console located within the residence may beaccomplished in a well known manner, and the remaining elements shown inFIG. I are provided in the control console.

Turning now to the system components shown in FIG. 1 a self-containedbattery pack 10 is provided to achieve a voltage potential between thelines L-l and L-2. A push to test switch 12 is provided to check thestatus of the battery when the key control lock switch 14 is turned onby an appropriately shaped key. A gallium arsenide light emitting diode16 is mounted on the console and adapted to be energized when the pushto test switch is closed and a resistive load is applied across thebattery as shown at 18. If the load resistor drops the battery voltagebelow horn operating specifications, the blocking zener 20 connected inseries with the light emitting diode 16 will not function below itsthreshold and the light will not indicate telling the occupant of thehouse to replace the battery as soon as possible.

A mode selector switch 22 is provided on the console, and permits theoccupant to select an in mode or an out mode. This selection will bedictated by virtue of whether the occupant intends to remain in hisresidence or to go out for any reason. For example, when the system isactivated at. night when the occupant retires for the evening, the modeselector switch 22 would be placed in the in position. The controlswitch 14 can be closed from the open position shown and a nine secondtime delay provided for last minute checking of doors and windows. Analarm will occur after a lapse of nine seconds if entry is attempted.The alarm device 24 is also provided in the console, and the sensingcircuit for operation of the horn 24 from the battery source 10 with themode selector switch in the in position will now be described in detail.

With the system turned on as described above battery voltage is appliedacross a time delay network consisting of a resistor R and capacitor CWhen a conventional 6 volt battery is used as the power source for atypical circuit, R preferably comprises a relatively large resistance asfor example 690K ohms. The capacitor C is chosen to have a capacitanceof 22 microfarads. When the capacitor C is fully charged the onlycurrent being drawn from the battery, will be due to minute capacitorleakage. The capacitor, when charged above the threshold voltage ofzener Z will provide a triggering voltage to a silicon control rectifierSCR, or solid state gate means through one or more of the sensingdevices which may have been closed as for example by an intruder inopening or otherwise tampering with a window or door. If one or more ofthe limit switches LS and LS are closed momentarily prior to the ninesecond time delay, achieved through the capacitive resistive groupingmentioned above, the zener threshold voltage level will not have beenreached, resulting in continual blocking of the triggering circuitassociated with the gate means SCR,. Thus, the occupant might closecontrol key switch 14, and subsequently close an exit door within thenine second time delay provided for, and no alarm willbe sounded.Capacitor C 9 preferably has a capacitance of .05 microfarads and servesonly to assure the proper operation of the triggering circuitrydescribed above. Resistor R serves to cooperate with the resistor R todefine a voltage dividing network in combination with the zener Z andone or more of the limit switches L8,, LS for a purpose to be describedin greater detail hereinbelow.

Once an intrusion occurs, and a limit switch such as LS closes,capacitor C discharges through the zener Z triggering the siliconcontrol rectifier SCR, allowing current to be conducted through this SCRgate, providing battery voltage in the line L with respect to the groundline L Resistor R serves to latch SCR in its conductive state. If thein" position of the mode switch 22 has been selected, the horn 24 willsound immediately or nearly so. A voltage dividing network is formed byresistors R and R through the mode switch 22 providing a triggeringvoltage for a unijunction transistor 26, charging of capacitor C in thisparticular mode of operation of the system is accomplished virtuallyinstantaneously due to the fact that resistor R comprises only 6,8Kohms. The unijunction transistor 26 comprises a threshold voltage devicewhich triggers a secondary gate means, in the form of silicon controlrectifier SCR to conduct with the result that the horn 24 will have oneside grounded by line L and the other side provided with six voltsthrough the line L,,. The resistor R associated with the vibrating horn24 allows its satisfactory operation, and

also serves to latch the gate SCR in its conductive state. Thus, in thecase of a forced entry, with the occupant in his residence, and the inposition of the mode switch selected, as mentioned above the alarm willsound virtually instantaneously following any intrusion. Actually, withthe capacitances and resistances mentioned above a delay time ofapproximately 1/ 10 of a second will occur. The operation of theabovedescribed circuitry in the out" mode position of selector switch 22will now be described.

Upon leaving this residence the occupant uses his key to close keycontrol switch 14 allowing capacitor C to charge as described above,with the resistor R serving to limit the current flow to approximately9p. amperes with the result that when capacitor C is fully charged a 9second delay will have occured. Within this 9 second delay the occupantmay open one of the secured exits, his front door for example if heintends to exit through the front door, and having opened one of thelimit switches, such as LS during this 9 second delay, no alarm willsound. This important feature of the present invention is possible byvirtue of the placement of the limit switches LS and LS between thezener Z and the gate means SCR As mentioned above a voltage dividingnetwork is formed consisting of resistor R zener Z one or more of thelimit switches LS, and resistor R,,, to prevent the capacitor C fromcharging above the required zener threshold voltage until one or theother limit switches, LS and LS for example, is again closed. In otherwords, the front door, or other exit through which the occupant intendsto leave his premises may be held open as long as desired. The systemonly being armed when this door is reclosed and capacitor C isrecharged.

Once this door is closed, the capacitor C is charged within the nineseconds mentioned above. The next entry will of coursevclose one or moreof the limit switches LS providing a discharge path for the capacitor Cthrough the zener Z triggering the silicon control rectifier gate SCR Asmentioned above, this will provide lines L and L at different potentialswith respect to one another with no time delay.

With the out mode of selector switch 22 selected resistor R with itslimited resistance of 6.8K ohms is out of circuit, and resistor R at270K ohms controls the charging of capacitor C. At the expiration of apredetermined time delay, dictated by this capacitor resistive group Cand R the unijunction transistor 26 will conduct triggering the gate SCRwhen the threshold voltage of the unijunction transistor is exceeded.The horn 24 will thus be grounded, and line L, will carry the audio hornto sound, resistor R serving not only to provide the necessary voltageon the intermittent horn device but also serving to latch the SCR in itsconductive state, and to retain this condition until key control switch14 is switched to its off position.

Assuming that the key control switch 14 is turned on with the modeswitch 22 in its out position the predetermined time delay mentioned inthe preceeding paragraph will allow the occupant to secure any open dooror window, after which time the alarm device will function so as tosound the alarm whenever an unauthorized entry closes one of the limitswitches LS, or LS or more particularly after the nine second delayfollowing such unauthorized entry. This latter 9 second delay isintended to allow the occupant to return to his residence, to open thedoor with his usual household key, and to give him 9 seconds withinwhich to get to the key control switch 14 and to turn it off. Onceturned off, the occupant can reclose the door by which he just entered,and switch the mode selector switch to the in position, and reclose thekey control switch 14 thereby activating the alarm system for thecontinued security of his residence.

A status check circuit is provided when the control switch 14 is firstturned on, a timing network consisting of capacitor C and resistor Rproviding a short duration pulse via the charging of the capacitor C tobe applied through diode D to the limit switches LS and LS If any suchswitch is closed, indicating that a door or window is not secure, apulse path is provided to the gate SCR The triggering of SCR will ofcourse initiate an alarm immediately if the mode switch is positioned toin. i v

The timing network pulse of capacitor C is also applied simultaneouslythrough diode D to a test circuit gate SCR Triggering gate SCR initiatesan effective bridge of the mode switch, permitting capacitor C to becharged in a reduced time since the normal timing network for triggeringSCR will have been parallelled by the combination of resistance R andresistance R leading to capacitor C Thus, this circuitry performs in thesame manner as the night in mode selector switch position. In conclusionthen, the status network described above in affect overrides the timedelay networks in both the primary sensing circuit and the secondarysensing circuit described above to provide an immediate audio alann ifany limit switch LS, or LS is closed indicating an unsecure condition ata door or window or the like.

We claim:

1. An alarm system comprising:

a. a source of electrical energy,

b. a sensing circuit having at least one sensing device with contactsadapted to close in response to a condition to be detected,

c. a control switch for connecting said sensing circuit to said source,

(1. an electrically energizable alarm device,

c. said sensing circuit further including selectively conductive solidstate gate means for operating said sensing circuit to said alarmdevice,

f. said sensing circuit further including a first gate triggeringnetwork which includes said sensing de- 5 vice contacts,

g. said gate triggering network including a capacitive resistance groupfor delaying said first gate from conducting for a first predeterminedtime delay,

h. second solid state gate means in said sensing circuit and including asecond triggering network which network includes a second capacitiveresistance group for delaying said second gate from conducting for asecond predetermined time delay, and

i. a mode switch forming a part of a paralleled resistive network toreduce said second delay when said mode switch is closed and to providesaid second time delay following closing .of said control switch and oneof said sensing device contacts when said mode switch is opened.

2. The alarm system of claim 1 further characterized by a voltagethreshold device in each of said gate triggering networks forcontrolling the voltage at which said gate is triggered by itsassociated capacitive resistance group.

3. The alarm system of claim 2 wherein at least one of said thresholddevices comprises a zener so arranged that when the capacitive portionof said group is charged above the threshold associated with said zener,triggering voltage is available at the first solid state gate means viathe closed contacts of said sensing device.

4. The alarm system of-claim 3 further characterized in that said modeswitch is more particularly located between said second threshold deviceand said second capacitive resistance group, and said parallelresistance network comprising a by-pass resistor so arranged as toincrease the rate at which the capacitance portion of said second groupis charged to the threshold voltage of said threshold device.

5. The alarm system of claim 4 further characterized by a sensing devicestatus check circuit which permits said first gate triggering network tobe by-passed in checking for closed contacts in said sensing devicewithout encountering said first delay.

Pat t N 3,803,576 Dated April 9, 1974 Inventor s John J. Dobrzanski andWilliam J. Doyle It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Inventor's name: Willgim J. Doyle should be WillEm J. Doyle C01. 1, line39, "be" should be --by--.

C01. 3, line 15, "6,8K" should be --6.8K--.

Signed and sealed this 1st day of October 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. 0. MARSHALL DANN Attesting Officer Commissioner ofPatents FORM powso (10-69) uscoMM-Dc 60376-P69 9 .5. GOVERNMENT 'RINTINGOFFICE I," 0-365'33,

1. An alarm system comprising: a. a source of electrical energy, b. asensing circuit having at least one sensing device with contacts adaptedto close in response to a condition to be detected, c. a control switchfor connecting said sensing circuit to said source, d. an electricallyenergizable alarm device, e. said sensing circuit further includingselectively conductive solid state gate means for operating said sensingcircuit to said alarm device, f. said sensing circuit further includinga first gate triggering network which includes said sensing devicecontacts, g. said gate triggering network including a capacitiveresistance group for delaying said first gate from conducting for afirst predetermined time delay, h. second solid state gate means in saidsensing circuit and including a second triggering network which networkincludes a second capacitive resistance group for delaying said secondgate from conducting for a second predetermined time delay, and i. amode switch forming a part of a paralleled resistive network to reducesaid second delay when said mode switch is closed and to provide saidsecond time delay following closing of said control switch and one ofsaid sensing device contacts when said mode switch is opened.
 2. Thealarm system of claim 1 further characterized by a voltage thresholddevice in each of said gate triggering networks for controlling thevoltage at which said gate is triggered by its associated capacitiveresistance group.
 3. The alarm system of claim 2 wherein at least one ofsaid threshold devices comprises a zener so arranged that when thecapacitive portion of said group is charged above the thresholdassociated with said zener, triggering voltage is available at the firstsolid state gate means via the closed contacts of said sensing device.4. The alarm system of claim 3 further characterized in that said modeswitch is more particularly located between said second threshold deviceand said second capacitive resistance group, and said parallelresistance network comprising a by-pass resistor so arranged as toincrease the rate at which the capacitance portion of said second groupis charged to the threshold voltage of said threshold device.
 5. Thealarm system of claim 4 further characterized by a sensing device statuscheck circuit which permits said first gate triggering network to beby-passed in checking for closed contacts in said sensing device withoutencountering said first delay.